Rigid rotor assembly for folding helicopter blades

ABSTRACT

Described herein is a rigid rotor assembly configured to allow rotation of helicopter rotor blades attached to the rigid rotor assembly from a deployed position to a stowed position. The rigid rotor assembly includes a base including a shaft extending therethrough, a first spindle configured to engage the shaft, and a second spindle configured for placement onto the shaft. The second spindle is operable to maintain a first position with respect to the first spindle via an attachment mechanism therebetween, the second spindle further operable to maintain a second position with respect to the first spindle via the attachment mechanism.

BACKGROUND

Large radial dimensions of helicopter rotor assemblies and the bladesassociated therewith result in helicopters having large structuralenvelopes that occupy an inordinate amount of space. It is oftendesirable to reduce the large structural envelopes of such helicoptersto facilitate rapid deployment, routine transport, stowage, and/or toreduce vulnerability of the helicopters to environmental conditions.

One current option available to reduce the structural envelopesassociated with helicopters is to design main rotors of helicopters sothat main rotor blades may be temporarily removed from a rotor hubassembly (i.e., a main rotor assembly). However, main rotors may beunnecessarily complex, and/or removal of the main rotor blades may betime consuming and labor intensive. Moreover, the same time constraintsand labor requirements also exist when the helicopter is reconfiguredfor subsequent flight operations. Further, a problem exists in thisconfiguration in that removal of the main rotor blades may require arebalancing of the blades upon reattachment.

Another option often used to reduce the structural envelopes ofhelicopters is to design main rotor assemblies and rotor blades so thatthe main rotor blades may be folded about the main rotor assembly.However, no such configuration is currently available because of uniquerequirements associated with rigid rotor assemblies.

Therefore a rigid rotor assembly is needed that allows main rotor bladesto be folded (e.g., rotated) from a deployed position to a stowedposition without a need for additional ground support equipment or aremoval of any of the main rotor blades.

SUMMARY

In one aspect, a rigid rotor assembly configured to allow rotation ofhelicopter rotor blades attached to the rigid rotor assembly from adeployed position to a stowed position is provided. The rigid rotorassembly includes a base comprising a shaft extending therethrough, afirst spindle configured to engage the shaft, and a second spindleconfigured for placement onto the shaft. The second spindle is operableto maintain a first position with respect to the first spindle via anattachment mechanism therebetween. The second spindle is also operableto maintain a second position with respect to the first spindle via theattachment mechanism.

In another aspect, a helicopter is provided. The helicopter includes aforward section, a tail section rearward of the forward section, and arigid rotor assembly. The rigid rotor assembly is configured to allowrotation of helicopter rotor blades attached to the rigid rotor assemblyfrom a deployed position to a stowed position. The rigid rotor assemblyincludes a first spindle attached to a rotor shaft, and a secondspindle. The second spindle has a hub opening operable for placing thesecond spindle onto the shaft and further includes an attachmentmechanism operable for maintaining the second spindle in a firstposition with respect to the first spindle and further operable formaintaining the second spindle in a second position with respect to thefirst spindle.

In still another aspect, a method for rotating helicopter rotor bladescoupled to a rigid rotor assembly from a deployed position to a stowedposition is provided. The method includes removing at least oneretention pin from a first aperture on a first spindle and a secondaperture on a second spindle, the first aperture being aligned with thesecond aperture, the spindles configured for attachment of rotor bladesthereto, rotating the first spindle about an axis of the rigid rotorassembly such that the first aperture on the first spindle is alignedwith a third aperture on the second spindle, and inserting the at leastone retention pin into the first aperture and the third aperture.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view of a helicopter having a rigid rotor assembly andfour main rotor blades in a deployed position.

FIG. 2 is a top view of a helicopter having a rigid rotor assembly andfour main rotor blades in a stowed position.

FIG. 3 is an exemplary rigid rotor assembly, without rotor blades,illustrated in a deployed configuration.

FIG. 4 is the exemplary rigid rotor assembly of FIG. 3 illustrated in astowed configuration.

FIG. 5 is a view of the exemplary rigid rotor assembly of FIG. 3 with anupper spindle removed.

DETAILED DESCRIPTION

The subject matter of the present disclosure is described withspecificity herein to meet statutory requirements. However, thedescription itself is not intended to limit the scope of the claimedsubject matter. Rather, the inventors have contemplated that the claimedsubject matter might also be embodied in other ways, to includedifferent steps or combinations of steps similar to the ones describedin this document, in conjunction with other present or futuretechnologies. Moreover, although the terms “step,” “block,” and/or“operation” may be used herein to connote different elements of methodsemployed, the terms should not be interpreted as implying any particularorder among or between various steps herein disclosed unless and exceptwhen the order of individual steps is explicitly described.

Referring now to the drawings, and more particularly to FIG. 1, ahelicopter is indicated in its entirety by reference numeral 50. Inembodiments, the helicopter 50 has a fuselage, generally indicated at52, including a forward section 54 and an aft section 56 (e.g., a tailsection) rearward of the forward section 54. The helicopter 50 furtherincludes a rigid rotor assembly, generally indicated at 58, extendingupwards from the forward section 54 of the fuselage 52, and at leastfour rotor blades coupled to the rigid rotor assembly 58 configured forrotation about a rigid rotor axis X_(r). In embodiments, the helicopter50 may include more than one rigid rotor assembly 58. In the illustratedembodiment, the rigid rotor assembly 58 includes four rotor blades, forexample, a first rotor blade 60, a second rotor blade 62, a third rotorblade 64, and a fourth rotor blade 66. However, embodiments thatincorporate fewer or additional rotor blades are contemplated. Inembodiments, the rigid rotor assembly 58 further includes a lowerspindle 302 and an upper spindle 304, which are described in additionaldetail below with respect to FIG. 3.

Continuing with FIG. 1, the four rotor blades 60, 62, 64, and 66 areillustrated in a deployed, or first, position. In embodiments, adeployed position is a position in which the rotor blades 60, 62, 64,and 66 are orientated such that the helicopter 50 is ready for flightoperations. For example, when in a deployed position, the first rotorblade 60 extends radially outwardly from the rigid rotor assembly 58generally in a first direction, the third rotor blade 64 extendsradially outwardly from the rigid rotor assembly 58 generally in asecond direction opposite the first direction. The second rotor blade 62extends radially outwardly from the rigid rotor assembly 58 generally ina third direction and the fourth rotor blade 66 extends radiallyoutwardly from the rigid rotor assembly 58 generally in a fourthdirection opposite the third direction. While the angle of separation ofthe two blade pairs is shown as being substantially perpendicular inthis embodiment, other embodiments may have substantially differentseparation angles, particularly when additional rotor blades areincorporated. Generally, when deployed for flight operations, the rotorblades are evenly spaced. For example, in the illustrated embodiment,and described above, the blades are spaced at 90 degree intervals. For asix blade configuration, the spacing would be at 60 degrees.

With reference now to FIG. 2, a top plan view of a helicopter having arigid rotor assembly 58 and the four main rotor blades 60, 62, 64, and66 in a stowed, or second, position is provided. In embodiments, whenthe four rotor blades 60, 62, 64, and 66 are in a stowed position, twoof the four rotor blades 60, 62, 64, and 66 extend generally in aforward direction (e.g., toward the forward section 54) and the othertwo of the four rotor blades 60, 62, 64, and 66 extend in a rearwarddirection (e.g., toward the aft section 56). One of ordinary skill inthe art will appreciate that a determination of which rotor blades willextend in a forward direction or which rotor blades will extend in arearward direction (i.e., aft rotor blades) may be made at anytimeduring a folding operation. For example, in a deployed position, tworearward-most rotor blades may become aft rotor blades and the twoforward-most blades become forward rotor blades. For exemplary purposes,as shown in FIG. 2, the first rotor blade 60 and the fourth rotor blade66 are aft rotor blades, and the second rotor blade 62 and the thirdrotor blade 64 are forward rotor blades. For simplicity, a foldingoperation of the first rotor blade 60 and the third rotor blade 64 willbe described herein in detail below, with reference to the rigid rotorassembly shown in FIG. 3.

FIG. 3 is an illustrative example of the rigid rotor assembly 58. Forclarity, the rotor blades 60, 62, 64, and 66 are not shown in FIG. 3. Inembodiments, the rigid rotor assembly 58 includes the lower spindle 302(which is sometimes referred to herein as a first spindle), the upperspindle 304 (which is sometimes referred to herein as a second spindle),and a housing 306 that covers a majority of shaft 307. In embodiments,the shaft 307 extends through a base 310 of the housing 306 and acylindrical portion of this shaft 307 extends through each of the lowerspindle 302 and the upper spindle 304. In embodiments, the lower spindle302 engages a portion of the shaft 307 via a spline interface (notshown) or other effective torque coupling mechanism. In other words whenthe shaft 307 rotates, the lower spindle 302 rotates along with theshaft 307. In further embodiments, the upper spindle 304 is maintainedin an axial position with respect to an upper end of the shaft 307through a nut 308 that is secured to the top of the shaft 307. In oneembodiment, the engagement between the nut 308 and the shaft 307 furthercreates a compression fit between the upper spindle 304 and the bottomspindle 302. That is, in embodiments, the upper spindle 304 includes ahub opening and slides over the shaft 307 and is compressed down ontothe lower spindle 302 by securing the upper spindle 304 to the shaftwith a nut 308. It should be noted that in such an embodiment, the upperspindle 304 is free to rotate with respect to the shaft 307 but for anyresistance to rotation resulting from the above described compressionfit.

In embodiments, the nut 308 is configured to screw on to the top of theshaft 307, engage the upper spindle 304 and further compress the upperspindle 304 against the bottom spindle 302. In further embodiments, thelower spindle 302 and the upper spindle 304 include an attachmentmechanism (e.g., pin receiving apertures and at least one pin) operablefor maintaining the upper spindle 304 in a deployed position withrespect to the lower spindle 302 and further operable for maintainingthe upper spindle 304 in a stowed position with respect to the lowerspindle 302. For example, the upper spindle 304 has at least one pinreceiving aperture 314 and the lower spindle 302 has at least two pinreceiving apertures 311 and 312. In the embodiment shown in FIG. 3, thelower spindle 302 includes pin receiving apertures 311 and 312, and theupper spindle 304 includes a pin receiving aperture 314. However, asFIG. 3 is only illustrative in nature, and due to the viewing angle ofFIG. 3, FIG. 3 illustrates only one pin receiving aperture (the pinreceiving aperture 314) on the upper spindle 304. However, in onespecific embodiment, a second pin receiving aperture is located at anopposite side of the upper spindle 304 from aperture 314. Further, FIG.3 illustrates only two pin receiving apertures (the pin receivingapertures 311 and 312) on the bottom spindle 302. However, in onespecific embodiment, two other pin receiving apertures are located atthe opposite side of the bottom spindle 304 and opposite respectiveapertures 311 and 312.

With continued reference to FIG. 3, the upper spindle 304 and the lowerspindle 302 are shown in a deployed position, for example, asillustrated in FIG. 1. An illustrative example of the rigid rotorassembly 58 in a stowed position is shown in FIG. 4. In embodiments,when in the deployed position, the pin receiving aperture 314 of theupper spindle 304 is aligned with the pin receiving aperture 312 of thelower spindle 302. In further embodiments, the upper spindle 304 is heldin the deployed position by inserting a retention pin 320 into the pinreceiving apertures 312 and 314. In this embodiment, a second pin wouldalso be inserted into the opposite pin receiving aperture on the upperspindle 304 and into an opposite pin receiving aperture on the bottomspindle 302. Embodiments that incorporate additional apertures and pinsare contemplated. Thus, the configuration of the rigid rotor assembly 58facilitates rapid insertion and removal of each retention pin 320 fromor into pin receiving apertures of the upper spindle 304 and the bottomspindle 302. Therefore, rotating two of the four rotor blades 60, 62,64, and 66 to and from a stowed position and a deployed positionrequires no additional ground support equipment or a removal of largecumbersome components.

With continued reference to FIG. 3, for simplicity, it will be assumedherein that rotor blades attached to the lower spindle 302, for example,the rotor blades 62 and 66, are currently in a stowed position. That is,in the current example, although all of the four rotor blades 60, 62,64, and 66 begin in a deployed position, the rotor blade 62 extends in aforwardly direction and the rotor blade 66 extends in a rearwardlydirection. Therefore, to place all of the four rotor blades 60, 62, 64,and 66 into a stowed position, only the first rotor blade 60 and thesecond rotor blade 64 need to be rotated. However, if the rotor blades62 and 66 attached to the lower spindle 302 are in a deployed positionand are not extending in a forwardly direction and a rearwardlydirection, one may manually or electrically rotate the rotor blades 62and 66 into a forwardly direction and a rearwardly direction. Inembodiments, to rotate the rotor blades attached to the upper spindle304, for example the rotor blades 60 and 64, into a stowed position (asshown in FIG. 5) from a deployed position, each retention pin 320inserted through each pin receiving aperture in the upper spindle 304 isfirst removed. For example, the retention pin 320 in the pin receivingapertures 312 and 314 is removed.

Once all of the retention pins 320 are removed, the rotor blades 60 and64 attached to the upper spindle 304 may be rotated between a deployedposition and a stowed position. Thus, the rotor blades 60 and 64attached to the upper spindle 304 are rotated about the rigid rotor axisX_(r) of the rigid rotor assembly 58. It is to be understood that eachof the first rotor blade 60 and the third rotor blade 64 are attached tothe upper spindle 304, therefore, each of the first rotor blade 60 andthe third rotor blade 64 are rotated between a deployed position and astowed position simultaneously in substantially the same manner. Thatis, because the first rotor blade 60 and the third rotor blade 64 areeach attached to the upper spindle 304, as the first rotor blade 60 isrotated between a deployed position and a stowed position, the thirdrotor blade 64 will also be rotated between a deployed position and astowed position.

In embodiments, and as shown in FIG. 4, once each of the first rotorblade 60 and the third rotor blade 64, and therefore the upper spindle304, are rotated into a stowed position, for example, when the pinreceiving aperture 314 of the upper spindle 304 is aligned with the pinreceiving aperture 316 of the lower spindle 302, a retention pin 320 isinserted into the pin receiving aperture 314 of the upper spindle 304and the pin receiving aperture 316 of the lower spindle 302 to hold thefirst rotor blade 60 and the third rotor blade 64 in the stowedposition.

With reference now to FIG. 5 an illustrative view of the rigid rotorassembly 58 is shown with the upper spindle 304 being removed from view.In embodiments, an upper spindle bearing 402 is included on the shaft307 and configured for rotational engagement with the upper spindle 304(not shown in FIG. 5). In one embodiment, the upper spindle bearing 402is separate from the shaft 307 and surrounds a portion of the shaft 306between the lower spindle 302 and the nut 308. In embodiments, the upperspindle bearing 402 is configured to reduce wear and tear on the shaft306 caused by a rotation of the upper spindle 304. FIG. 5 alsoillustrates a third pin receiving aperture 416.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to practice the invention, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe invention is defined by the claims, and may include other examplesthat occur to those skilled in the art. Such other examples are intendedto be within the scope of the claims if they have structural elementsthat do not differ from the literal language of the claims, or if theyinclude equivalent structural elements with insubstantial differencesfrom the literal languages of the claims.

1. A rigid rotor assembly configured to allow rotation of helicopterrotor blades attached to the rigid rotor assembly from a deployedposition to a stowed position, the rigid rotor assembly comprising: a) abase comprising a shaft extending therethrough; b) a first spindlecomprising a first aperture, the first spindle configured to engage theshaft, the first spindle further configured to have a first plurality ofrotor blades attached thereto; and c) a second spindle comprising asecond aperture and a third aperture, the second spindle configured tohave a second plurality of rotor blades attached thereto, the secondspindle further configured for placement onto the shaft, the secondspindle operable to maintain the second plurality of rotor blades in adeployed position with respect to the first plurality of rotor bladesvia a first retention pin inserted through the first aperture and thesecond aperture, the second spindle further operable to maintain thesecond plurality of rotor blades in a stowed position with respect tothe first plurality of rotor blades by removing the first retention pinfrom the first aperture and the second aperture and inserting the firstretention pin or a second pin through the first aperture and the thirdaperture.
 2. The rigid rotor assembly according to claim 1, wherein: theshaft comprises a spline formed thereon; and the first spindle isconfigured to engage the spline formed on the shaft.
 3. The rigid rotorassembly according to claim 1, wherein the shaft further comprises a nutconfigured to ensure retention of the first spindle and the secondspindle to the shaft under flight loading.
 4. A helicopter comprising: aforward section; a tail section rearward of the forward section; and arigid rotor assembly configured to allow rotation of helicopter rotorblades attached to the rigid rotor assembly from a deployed position toa stowed position, the rigid rotor assembly comprising: a first spindleattached to a rotor shaft, the first spindle comprising a firstplurality of rotor blades attached thereto and a first aperture; and asecond spindle, the second spindle comprising a second plurality ofrotor blades attached thereto, a second aperture, a third aperture, anda hub opening operable for placing the second spindle onto the shaft,the second spindle operable for maintaining the second plurality ofrotor blades in a deployed position with respect to the first pluralityof rotor blades by inserting a first retention pin through the firstaperture and the second aperture, the second spindle further operablefor maintaining the second plurality of rotor blades in a stowedposition with respect to the first plurality of rotor blades by removingthe first retention pin from the first aperture and the second apertureand inserting the first retention pin or a second retention pin throughthe first aperture and the third aperture.
 5. The helicopter accordingto claim 4, wherein the first spindle is attached to the shaft via aspline.
 6. The helicopter according to claim 4, wherein the shaftfurther comprises a nut configured to ensure retention of the firstspindle and the second spindle to the shaft under flight loading.
 7. Amethod for rotating helicopter rotor blades coupled to a rigid rotorassembly from a deployed position to a stowed position, the methodcomprising: removing at least one retention pin from a first aperture ona first spindle and a second aperture on a second spindle, the firstaperture being aligned with the second aperture, the spindles configuredfor attachment of rotor blades thereto; rotating the first spindle aboutan axis of the rigid rotor assembly such that the first aperture on thefirst spindle is aligned with a third aperture on the second spindle;and inserting the at least one retention pin into the first aperture andthe third aperture.
 8. The method according to claim 7, wherein:alignment of the first aperture and the second aperture is operable toplace rotor blades associated with the spindles into a deployedposition; and alignment of the first aperture and the third aperture isoperable to place rotor blades associated with the spindles into astowed position.
 9. The method according to claim 8, wherein the stowedposition describes a first portion of the rotor blades extendinggenerally toward a forward section of a helicopter and a second portionof the rotor blades extending generally toward a tail section of thehelicopter.